Television antenna



Dec. 30, 1952 TELEVISION O. M D. WOODWARD, JR

ANTENNA Filed Jan. 26, 1949 INVENTOR bakleyzlg Woad wardfi ALL Milk AORNEY Patented Dec. 30, 1952 S PATENT "OFFICE TELEVISION ANTENNA OakleyMcDonald Woodward, J r., Princeton, N. J assignor to Radio Corporationof America, a

corporation of Delaware Application January 26, 1949, Serial No. 72,974

12 Claims.

' evision channels.

The presently assigned television channels are spread over two bands,the lower band comprising channels 2-6 lying between 54 and 88 mc. s.,and the higher band comprising channels 7-13 lying between 174 and 216mc./s. It has been found that really satisfactory reception over bothbands with known antenna systems is accomplished only by employing twoseparate receiving antennas and complementary transmission lines.Alternately, the antenna for the higher band is connected to thetransmission line for the lower band antenna for fairly satisfactoryreception in some installations, though the efficiency of the system islowered to some considerable extent because of interaction.

It is an object of the invention to provide a simple antenna systemoperable over a. wide frequency range.

A more specific object of the invention is to .provide'an antenna systemcomprising a lower band antenna and a higher band antenna to be coupledto a receiver by a'feed system and providing uniform, highly efficientresults over all twelve of the presently assigned television fre 1quency channels.

It is another object of the invention to provide an antenna system forhome installations that is mechanically strong but light in weight andpleasing in appearance.

It is a further object of the invention to provide an antenna systemaffording optimum results over the entire band of twelve channelswithout any adjustment after installation is completed,

It is still another object of the invention to provide an antenna arrayhaving a bi-directional characteristic over all twelve channels.

These and other objects of the invention which will appear as thespecification progresses are achieved by means of a pair of antennasarranged to prevent interaction between each other and adapted to becoupled to a receiver by means of a feed system which effectivelyisolates the antennas from each other and nullify the effect of one whenreceiving on the other.

The invention will be described with reference to the accompanyingdrawing forming a part of the specification and in which:

Fig. 1 is an illustration of an antenna system according to theinvention; and

Fig. 2 is a schematic diagram of the electrical connections of theantenna system shown in Fig. 1.

Referring to Fig. 1 there is shown a support II on which is mounted ablock member I2 having rod members I3 and I4 affixed thereto normally tothe axis of support I I and a further insulating mounting member l5afiixed. to One side satisfactory results.

2 of block member I2. The members thus. .far described need not beformed exactly as shownin the figure but may be constructed in anymanner suggested to one working in the art as the.configurations ofthese members are not: important to the invention. At the outer. ends ofmembers I3 and I4, folded dipole elements 2| arearranged. Furtherdetails of construction and operation -of these folded dipole elementsmay be had by referenoe to U. S. Patent 2,283,914 issued May 26, 1942,to Philip S. Carter and assigned to the Radio Corporation of America.The high impedance terminals 22 and 23 are electrically insulated andmechanically fixed by means of low loss dielectric insulation 24. Asexplained in the above mentioned U. S. patent, little or no loss will beeffected at the portion of the folded diploe element opposite theterminals if it is electrically connected to a metallic support, hencerod members I3 and I 4 may be made of any conducting material desired,and preferably are in most installations. Preferably, folded dipoleelements H are adjustable by means of trombone endsecti'ons 25 althougha fixed construction resonant to a frequency near the center of thehigher television band may be used with entirely Midway between foldeddipole 2| a double V" element comprising arms 3I, 32, 33, and 34"isfastened to mounting member I5 by means of metal plates 35-and 36. Arms3I and 32 arranged at an angle of approximately and electricallyconnected to plate 35 and arms 33 and 34, are arranged at the same angleand connected to plate 36, which plates form the terminals for thedouble-V element. In the preferred embodiment, plates 35 and 35 aremechanically fastened to insulating member I5, which is in turn fastenedto a metallic block IZ-in order to obtain maximum mechanical strength;however, if block I2 is made of low loss dielectric material, plates 35and 36 may be fastened thereto directly, eliminating any need for anadditional member I5.

By means of insulating rings 49 mounted on support I I by means ofclamps 4|, a transmission line 42 leading to a receiver or othertransducer (not shown) is brought to the antenna system. At a suitablepoint along support I I transmission line 42 is electrically connectedin parallel to further transmission lines 44, 48, and 49. Transmissionlines 48 and 49 are equal in length and terminate at folded dipoles 2 I,while transmission line 44 terminates at terminal plates 35 and 33 ofthe double-V element for a purpose later to be described. This line isfolded and fastened in place on rod members 4 by any convenient means,such as rubber tape or suitable metal clamps, to prevent it fromwhipping in the wind. Preferably some means of protection againstlightning should be provided in any antenna in stallation and thearrangement according to the invention readily lends itself to thispurposeas shown in Fig. 1 wherein a lightning rod 5| is clamped to ametal support H by means of clamps .52.

Further details of the construction of the antenna system according tothe invention will most conveniently appear as the operation of thesystem is described with reference to Fig. 2,

schematically showing the electrical connections tween" the. two;arraysis; prevented because. of the I factathatrthe folded: dipole"elements 21 are. connectedxoutofphase with each other by means oftransmissionlines lt and.49.-as;can be seen more clearly in Fig. 2,where folded. dipole elements 21'- are connected by, lines at. and 49 intransposed relationship,.and the..doublev array lies in a neutral planemidway between the folded dipole array, thus. preventing extraneous sidelobes from appearing at the higher frequencies.

It should-be understood that the antenna systemas expressly'describedmerely constitutes an example of an arrangement'according, to the in- 1;

ventionand: other arrangements will be immediately suggestedto-theartisan. For example,

the-ordinary dipole may be substituted for the.

doublew dipole, aoonicaldipole antenna may be. equally well employed; orin other words any broadside antenna capable of being confined to a.neutral. zone midway between the elements of the end-fire array, but notnecessarily inv line withrtheend fire elements, will serve to effectanarrangement according to the basic. principle of the. invention.Accordingly any end. fire array whichwillprovidezsuch aneutral zone willfulfill therequirements. of an arrangement according to. the invention;In addition, it should be obvious that the endfire. array may be used inthe lower band and the broadside antenna on the higher-band also withoutdeparting from the invention; It should be understood that the termbroadside array must be construed in this specification to includesingle elements such as the ordinary dipole as wellas-multi-elementarrayssince the invention uniquely lends itself. to the use of both.Preferably, all. of. the transmission line seeticnshave thesamecharacteristic. impedance, though it. is entirely possible touse.sections of different characteristicimpedance together with suitabletransformer sections and remain within the scope of the invention. Sincemost commercially produced television receivers are designed. for 300ohminput transmissionlineawhioh are. readily obtainable in quantity, itis preferable to employ 300 ohm lines throughout andthusavoiddiffioultiesin matching linesof varying characteristicimpedances;

Transmission line 48 is a quarterwave long at the-center of the highfrequency band (195 mc./s.

for: the presently allotted channel) and thus short circuits theterminals of the double-V arrayv at. the higher frequencies.Transmission line 44 is also a quarterwavelong atv the. higherfrequencies and. thus presents an infinite impedance. (or open circuit).to the junction point C oftransmissionlines 42, 44, 48, and 4% Hencewhen signals on. the. higher frequency channels arereceived, onlythe-foldeddipole array is effective.

At the lower frequencies, however, folded dipole 2i functions as twoshort circuited stubs, B and B, connected in series. Transmission lines43 and 59 are of such length as to present a high reactance at point'C.Transmission line it will have little effect on the double-V array whensignals at the lower frequencies are received. Hence, when lower bandsignals are received, only the double-V array is effective.

The antenna system as described provides substantiallyfigure-eight-field patterns in the same direction in. the azimuthalplanefor the twelve presently allotted. televisionohannela It is alsopossible to. provide-a somewhat. different-directivity for the lowfrequency band. withrespectto the high, frequency band by varying theazimuthal position. of. one of. theantennas with respect to the other,carev being, taken thatthe broadside array is sci arranged. with.respect to the endfire array that equal and opposite voltages areinduced in one by the-other.

While the invention has been described in terms of. express embodiments,it is to be understood. that obvious modifications thereof will besuggested to. thoseskilledin. the art without departing-fromthespirit-andscope of the invention.

I claim 1. A. lei-directional antenna. system includingan-element-resonant to a firstfrequency, and other elements resonant to.a. second. frequency arranged equidistantly on either. side of the.first said element, said other elementsbeing coupled to each other inphase opposition, the first said element and said other elements beingelectrically independent of each other, and means to connect transducerapparatus to the first said element and said other elements and maintainsaid electrical independence. therebetween.

2. An. antenna systemincluding an antenna resonant to a first frequencyand comprising two elements intercoupled by a pair of conductors toprovide an end-fire array, an antenna resonant to a second frequency andelectrically equidistant from each of the elements of said first antennawhereby interaction between said antennas is prevented, a length oftransmission line, a multiple, including unity, of a half wave lengthlong at said first frequency coupled at one end to the pair ofconductors of said first antenna and coupled at the midpoint thereof tosaid second antenna, and; means to couple transducer apparatus to thesystem at said one. end of said length of transmission line.

3. A bi-directibnal antenna system? including an antenna resonant to afirst frequency and comprising'two elements intercoupled by transmissionline means to provide an end-fire array, an antenna resonant to a secondfrequency and located electrically equidistant from the elements ofsaidfirst' antenna whereby interaction between said antennas isprevented, a length of transmission line, a multiple, including unity,of a half wave length long at said first frequency at one end to saidtransmission line, means of said first antenna and coupled at themidpoint thereof to said second antenna, and means to coupletransducerapparatus tothe system atsaid'one end of said-length of transmissionline, said transmission line means intercoupling said two elementshaving a length at which a high reactan'ce is presented at said one endof said length of transmission line.

4. An.- antemia system including an antenna resonant to a firstfrequency, said antenna comprising two elements and a transmission lineintercoupled to provide an end-fire array, an antenna resonant to asecond frequency and located between the elements of said first antennaat a point electrically equidistant from each of said elements wherebyinteraction between said antennas is prevented, a further transmissionline a half wave length long at said first frequency coupled at one endto the midpoint of said first transmission line and coupled at themidpoint thereof to said second antenna, and means to couple transducerapparatus to the system at said one end of said further transmissionline, said first transmission line having a high reactance at themidpoint thereof at said first frequency.

5. An antenna system including dipole elements resonant to a firstfrequency, other dipole elements resonant to a second frequency arrangedequidistantly on either side of the first said dipole elements, saidother dipole elements being coupled to each other in phase oppositionand coupled to the first said dipole elements in phase opposition atsaid second fre uency, and means effectively to short circuit the firstsaid dipole elements at said second frequency.

6. An antenna system including dipole elements resonant to a firstfrequency, other dipole elements resonant to a second frequency arrangedequidistantly on either side of the first said dipole elements,transmission line elements coupled at one end to said other dipoleelements and coupled to each other at the other ends to couple saidother dipole elements in phase opposition, and transmission linesections coupled to the first said di ole elements, one of saidtransmission line sections being coupled to the junction of saidtransmission line elements, said transmission line elements havinglengths at which a high reactance at said second frequency is presentedat said function and said transmission line sections having lengths atwhich the first said dipole elements are short circuited at said secondfrequency.

7. An antenna system including a pair of folded dipoles resonant to afirst frequency and arranged parallel to each other and spaced apart, adipole antenna resonant to a second frequency and havin two arms eachcomprising conductor elements diverging from the center thereof, saidelements being arranged parallel to said folded dipoles and located at apoint intermediate said folded dipoles. a length of transmission linecoupling said folded dipoles out of phase with each other, atransmission line having a length of onequarter wave length at saidfirst frequency coupling said dipole antenna to the midpoint of thefirst said transmission line, and means to couple said midpoint totransducer apparatus.

8. An antenna system including a pair of folded dipoles resonant to agiven frequency and arranged parallel to each other and spaced apart, adipole antenna resonant to a frequency lower than said given frequencyand having two arms each comprising V-shaped conductor elements, saidelements being arranged parallel to and located at a point intermediatesaid folded dipoles, a length of transmission line coupling said foldeddipoles out of phase with each other, a transmission line having alength of one-half wave length at said given frequency coupled to themidpoint of said length of transmission line, said dipole antenna beingconnected to the midpoint of said halfwave line, and means to coupletransducer apparatus to said system at the junction of said length oftransmission line and said halfwave line.

9. An antenna system including a pair of folded dipoles resonant to agiven frequency and arranged parallel to each other and spaced apart, adipole antenna resonant to a frequency different from said givenfrequency and having two arms each comprising V-shaped conductorelements, said elements being arranged parallel to and located at apoint intermediate said folded dipoles, a length of transmission linecoupling said folded dipoles out of phase with each other, atransmission line having a length of one-half wave length at said givenfrequency coupled to the midpoint of said length of transmission line,said dipole antenna being connected to the midpoint of said halfwaveline, and means to couple transducer apparatus to said system at thejunction of said length of transmission line and said halfwave line.

10. An antenna system including two separate antennas, one of saidantennas being resonant to a given frequency and comprising two dipoleelements arranged substantially parallel to each other and coupled inphase opposition, and the other antenna being resonant to a differentfrequency and being arranged substantially in between said dipoleelements and electrically equidistant from each of said two dipoleelements thereby effectively to neutralize electrical coupling betweensaid antennas, and means to couple a transducer to both of said antennaswhile maintaining said antennas operable individually at each of saidfrequencies.

11. An antenna system including an end-fire array comprising an evennumber of elements and resonant at a given frequency and a dipoleantenna array resonant to a different frequency and arrangedsubstantially in between and electrically equidistant from the outermost elements of said end-fire array, and means to couple a transducerto both of said arrays while maintaining said arrays operableindependently of each other.

12. An antenna system including two separate antennas, one of saidantennas comprising two folded dipoles resonant at a given frequency andarranged substantially parallel to each other and coupled in phaseopposition, and the other antenna comprising a dipole element resonantto a different frequency and located substantially in between andelectrically equidistantly between said two folded dipoles, therebyeffectively to neutralize electrical coupling between said antennas, andmeans to couple a transducer to both of said antennas while effectivelyelectrically isolating one antenna from the other OAKLEY MCDONALDWOODWARD, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,064,774 Wheeler Dec. 15, 19362,413,951 Carter Jan. 7, 1947 2,425,887 Lindenblad Aug. 19, 1947 FOREIGNPATENTS Number Country Date 532,955 Great Britain Feb. 4, 1941 OTHERREFERENCES Radios Master, 12th ed., page 40, May 9, 1947.

